Mr Berezovsky, 65, said Mr Abramovich, 45, had intimidated him into selling shares in Russian oil giant Sibneft. He was claiming £3bn ($4.7bn) in damages.

But the London Commercial Court judge said Mr Berozovsky had been an "inherently unreliable" witness.

Mr Berezovsky said he was "shocked" at Mrs Justice Gloster's decision and that she had rewritten Russian history.

The BBC estimates the total legal costs in the case are up to £100m.

In her ruling the judge said: "On my analysis of the entirety of the evidence, I found Mr Berezovsky an unimpressive, and inherently unreliable, witness, who regarded truth as a transitory, flexible concept, which could be moulded to suit his current purposes."

She said she dismissed Mr Berezovsky's claims in relation to Sibneft - and a claim Mr Abramovich had broken a promise over a deal involving Russian aluminium company RusAl - "in their entirety".

She also said she found Mr Abramovich "to be a truthful, and on the whole reliable, witness".

'Political godfather'

Mr Berezovsky, who had told reporters before the verdict that: "I believe in the system", afterwards said : "I am absolutely amazed by what's happened today... particularly because Lady Gloster took the responsibility to rewrite Russian history."

Analysis

By Maria VassilievaBBCRussian.com

The trial was barely covered by Russia's main television channels or financial newspapers. Instead, it attracted attention in the country's business circles.

The case focused on one of the most shadowy periods of modern Russian history, when the majority of the country's billionaires started to accumulate their capital.

The informal link between business and power that existed in post-Soviet Russia has always been well-rumoured, but the detailed open hearing in London made them public, and turned guesswork into fact.

Many within the Russian business community welcomed the judge's decision to dismiss Mr Berezovsky's claims. The Russian president's spokesperson said: "It is pleasant, when libel is called libel."

Asked if he felt Russia's President Vladimir Putin would be happy with the ruling, he replied: "Sometimes I have the impression that Putin himself wrote this judgment."

He said he did not regret bringing the case against Mr Abramovich and did not know if he would appeal, adding: "I was absolutely shocked... but life is life."

The BBC's Moscow correspondent Daniel Sandford said there had been a lot of interest in the case in Russia as it shed light on the controversial sale of Russia's mineral wealth by the state to a small group of oligarchs in the early 1990s.

Mr Abramovich was not in court for the ruling and is thought to be in Monte Carlo for Chelsea's Super Cup Final on Friday night.

But a statement issued on his behalf said: "There were many serious allegations made against Mr Abramovich by Mr Berezovsky, including attacks on Mr Abramovich's honesty and integrity.

"We are pleased that the judge has firmly rejected all such allegations and has described Mr Abramovich as a truthful and frank witness who showed a responsible and honest approach when giving evidence in this case."

When he gave evidence, Mr Abramovich had said Mr Berezovsky was paid millions of pounds for his services as a "political godfather" but was not a business partner.

The court heard Mr Berezovsky "fled Russia, never to return" in 2000, after falling out with President Vladimir Putin.

Both men have homes in London, with Mr Abramovich owning a property in Knightsbridge as well as a 400-acre estate in Fyning, West Sussex.

'Power broker'

During the three-month trial, the court heard details of the lifestyles of Russia's super-rich oligarchs.

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Media captionThe BBC's Daniel Sandford on how the two men gained such wealth

Mr Berezovsky claimed Mr Abramovich was a "gangster" while Mr Abramovich responded by saying there were times when Mr Berezovsky was "something of a megalomaniac".

The hearing was told Mr Abramovich bought a businessman a plane to say thank you after one deal.

Mr Berezovsky told the court he was born in Moscow, studied mechanics and mathematics and worked as a designer for Russian state car maker AvtoVAZ in the 1970s, before going into business in the 1980s.

BATTLE OF THE OLIGARCHS TRIAL

Mr Abramovich objected about the hearing taking place in the UK, claiming it was "essentially Russian claims arising out of a uniquely Russian story"

The trial used new technology, called MagnumCloud, which gave the judge and lawyers secure access to documents from computers in the courtroom

The Queen spent several minutes in the courtroom where the case was heard during a visit in December when she chatted to Mrs Justice Gloster

In the 1990s, following the collapse of communism, Mr Berezovsky embarked on a political career and Mr Abramovich's lawyers claimed he was a "power broker" and a "highly controversial figure".

The hearing was told Mr Berezovsky's expenses - including "palaces in France", "private aircraft", "valuable paintings" and "jewellery for his girlfriend" - were paid for by Mr Abramovich.

Meanwhile, the case has been followed carefully by Russia's business community.

Commenting on the ruling, Alexandr Shokhin, head of Russian Unions of Industrialists and Entrepreneurs, said: "It's a good signal for all Russian businessmen and also power structures - highlighting that all relations should be built lawfully, on paper, and witnessed by reliable and independent witnesses."

But Vadim Malkin of Transitional Markets Consultancy said: "It's bad news for Russian business. The court in fact has proven that the majority of assets owned by the country's oligarchs have very questionable origins."